We study the seasonal and geographical variability of the peak electron density and the altitude of the main ionospheric peak at Mars. For this purpose, we use the data obtained by the ESA Mars Express mission, namely by the radar MARSIS and the radio occultation experiment MaRS. The accumulation of data during the long lifetime of Mars Express provides for the first time an almost complete seasonal and geographical coverage. We first remove the dominant variability factors affecting the main ionospheric peak, namely the effect of changes in the solar zenith angle (SZA), and the changes in the solar ultraviolet radiation output at the Sun. When averaging results obtained at all latitudes, we find that the seasonal variation of both the peak density and the peak altitude can be well reproduced by sinusoidal functions with amplitudes about 8%–9% of the annually averaged peak density, and between 8 and 9.5 km for the peak altitude. We also find elevated peak electron densities in the region of strong crustal fields and latitudinal asymmetries in both the peak density and altitude. Comparing the seasonal evolution of the peak altitude during Mars Year 28, a year with a global dust storm, and the rest of the years, we find that the global dust storm raised the altitude of the ionospheric peak by about 10–15 km.

中文翻译：

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火星快报观测结果显示火星电离层的季节和地理变异

我们研究了火星上电子密度峰值和电离层主峰高度的季节性和地理变异性。为此，我们使用ESA火星快车任务获得的数据，即雷达MARSIS和无线电掩星实验MaRS所获得的数据。Mars Express使用寿命长的数据积累首次为季节和地理范围提供了几乎完整的信息。我们首先删除影响电离层主峰的主要可变性因素，即太阳天顶角（SZA）的变化以及太阳输出的太阳紫外线辐射的变化的影响。当平均在所有纬度获得的结果时，我们发现，正弦函数可以很好地再现峰值密度和峰值高度的季节变化，其幅度约为年平均峰值密度的8％–9％，峰值高度在8至9.5 km之间。我们还发现，在强地壳区域和峰值密度和高度上的纬度非对称性区域，峰值电子密度都升高了。将火星在第28年，全球沙尘暴和其他年份的高峰高度的季节性变化进行比较，我们发现全球沙尘暴将电离层峰值的高度提高了约10-15 km。我们还发现，在强地壳区域和峰值密度和高度上的纬度非对称性区域，峰值电子密度都升高了。将火星在第28年，全球沙尘暴和其他年份的高峰高度的季节性变化进行比较，我们发现全球沙尘暴将电离层高峰的高度提高了约10-15 km。我们还发现，在强地壳区域和峰值密度和高度上的纬度非对称性区域，峰值电子密度都升高了。将火星在第28年，全球沙尘暴和其他年份的高峰高度的季节性变化进行比较，我们发现全球沙尘暴将电离层峰值的高度提高了约10-15 km。